Polycrystalline compacts including nanoparticulate inclusions, cutting elements and earth-boring tools including such compacts, and methods of forming same

ABSTRACT

A polycrystalline compact comprises a plurality of grains of hard material and a plurality of nanoparticles disposed in interstitial spaces between the plurality of grains of hard material. The nanoparticles have cores of a first material and at least one oxide material on the cores. An earth-boring tool comprises such a polycrystalline compact. A method of forming a polycrystalline compact comprises combining a plurality of hard particles with a plurality of nanoparticles to form a mixture and sintering the mixture to form a polycrystalline hard material comprising a plurality of interbonded grains of hard material. A method of forming a cutting element comprises infiltrating interstitial spaces between interbonded grains of hard material in a polycrystalline material with a plurality of nanoparticles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/277,010, filed Oct. 19, 2011, pending, which application claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/408,268,filed Oct. 29, 2010, titled “Polycrystalline Compacts IncludingNanoparticulate Inclusions, Cutting Elements and Earth-Boring ToolsIncluding Such Compacts, and Methods of Forming Same,” the disclosure ofeach of which is incorporated herein in its entirety by this reference.

FIELD

The present invention relates generally to polycrystalline compacts,Which may be used, for example, as cutting elements for earth-boringtools, and to methods of forming such polycrystalline compacts, cuttingelements, and earth-boring tools.

BACKGROUND

Earth-boring tools for forming wellbores in subterranean earthformations generally include a plurality of cutting elements secured toa body. For example, fixed-cutter earth-boring rotary drill bits (alsoreferred to as “drag bits”) include a plurality of cutting elementsfixedly attached to a bit body of the drill hit, Roller coneearth-boring rotary drill bits may include cones mounted on bearing pinsextending from legs of a bit body such that each cone is capable ofrotating about the bearing pin on which it is mounted. A plurality ofcutting elements may be mounted to each cone of the drill bit. In otherwords, earth-boring tools typically include a bit body to which cuttingelements are attached.

The cutting elements used in such earth-boring tools often includepolycrystalline diamond compacts (often referred to as “PDCs”), whichact as cutting faces of a polycrystalline diamond material.Polycrystalline diamond material is material that includes interbondedgrains or crystals of diamond material. In other words, polycrystallinediamond material includes direct, inter-granular bonds between thegrains or crystals of diamond material. The terms “grain” and “crystal”are used synonymously and interchangeably herein.

PDC cutting elements are typically formed by sintering and bondingtogether relatively small diamond grains under conditions of hightemperature and high pressure in the presence of a catalyst (e.g.,cobalt, iron, nickel, or alloys and mixtures thereof) to form a layer(referred to as a compact or “table”) of polycrystalline diamondmaterial on a cutting element substrate. These processes are oftenreferred to as high-temperature/high-pressure (HTHP) processes. Thecutting element substrate may comprise a cermet material (i.e., aceramic-metal composite material) such as, for example, cobalt-cementedtungsten carbide. In such instances, the cobalt (or other catalystmaterial) in the cutting element substrate may diffuse into the diamondgrains during sintering and serve as a catalyst material for forming theinter-granular diamond-to-diamond bonds, and the resulting diamondtable, from the diamond grains. In other methods, powdered catalystmaterial may be mixed with the diamond grains prior to sintering thegrains together in an HUT process.

Upon formation of a diamond table using an HTHP process, catalystmaterial may remain in interstitial spaces between the grains of diamondin the resulting PDC. The presence of the catalyst material in thediamond table may contribute to thermal damage in the diamond table whenthe cutting element is heated during use, due to friction at the contactpoint between the cutting element and the formation.

PDC cutting elements in which the catalyst material remains in the PDCare generally thermally stable up to a temperature of about 750° C.,although internal stress within the cutting element may begin to developat temperatures exceeding about 350° C. This internal stress is at leastpartially due to differences in the rates of thermal expansion betweenthe diamond table and the cutting element substrate to which it isbonded. This differential in thermal expansion rates may result inrelatively large compressive and tensile stresses at the interfacebetween the diamond table and the substrate, and may cause the diamondtable to delaminate from the substrate. At temperatures of about 750° C.and above, stresses within the diamond table itself may increasesignificantly due to differences in the coefficients of thermalexpansion of the diamond material and the catalyst material within thediamond table. For example, cobalt thermally expands significantlyfaster than diamond, which may cause cracks to form and propagate withinthe diamond table, eventually leading to deterioration of the diamondtable and ineffectiveness of the cutting element.

Furthermore, at temperatures at or above about 750° C., some of thediamond crystals within the polycrystalline diamond compact may reactwith the catalyst material causing the diamond crystals to undergo achemical breakdown or back-conversion to another allotrope of carbon(e.g., graphite) or another carbon-based material. For example, thediamond crystals may graphitize at the diamond crystal boundaries, whichmay substantially weaken the diamond table. In addition, at extremelyhigh temperatures, some of the diamond crystals may be converted tocarbon monoxide and/or carbon dioxide.

In order to reduce the problems associated with differential rates ofthermal expansion and chemical breakdown of the diamond crystals inpolycrystalline diamond compact cutting elements, so-called “thermallystable” polycrystalline diamond compacts (which are also known asthermally stable products, or “TSPs”) have been developed. Such athermally stable polycrystalline diamond compact may be formed byleaching the catalyst material (e.g., cobalt) out from interstitialspaces between the interbonded diamond crystals in the diamond tableusing, for example, an acid or combination of acids (e.g., aqua regia).All of the catalyst material may be removed from the diamond table, orcatalyst material may be removed from only a portion thereof. Thermallystable polycrystalline diamond compacts in which substantially allcatalyst material has been leached out from the diamond table have beenreported to be thermally stable up to temperatures of about 1,200° C. Ithas also been reported, however, that such fully leached diamond tablesare relatively more brittle and vulnerable to shear, compressive, andtensile stresses than are non-leached diamond tables. In addition, it isdifficult to secure a completely leached diamond table to a supportingsubstrate. In an effort to provide cutting elements havingpolycrystalline diamond compacts that are more thermally stable relativeto non-leached polycrystalline diamond compacts, but that are alsorelatively less brittle and vulnerable to shear, compressive, andtensile stresses relative to fully leached diamond tables; cuttingelements have been provided that include a diamond table in which thecatalyst material has been leached from a portion or portions of thediamond table. For example, it is known to leach catalyst material fromthe cutting face, from the side of the diamond table, or both, to adesired depth within the diamond table, but without leaching all of thecatalyst material out from the diamond table.

BRIEF SUMMARY

In some embodiments, a polycrystalline compact comprises a plurality ofgrains of hard material and a plurality of nanoparticles disposed ininterstitial spaces between the plurality of grains of hard material.The plurality of nanoparticles has a thermal conductivity less than athermal conductivity of the plurality of grains of hard material.

In additional embodiments, an earth-boring tool comprises apolycrystalline compact. The polycrystalline compact has a plurality ofgrains of hard material and a plurality of nanoparticles disposed ininterstitial spaces between the grains of hard material. The pluralityof nanoparticles has a thermal conductivity less than a thermalconductivity of the plurality of grains of hard material.

A method of forming a polycrystalline compact comprises combining aplurality of hard particles and a plurality of nanoparticles to form amixture and sintering the mixture to form a polycrystalline hardmaterial comprising a plurality of interbonded grains of hard material.The plurality of nanoparticles have a lower thermal conductivity thanthe plurality of hard particles.

A method of forming a cutting element comprises infiltratinginterstitial spaces between interbonded grains of hard material in apolycrystalline material with a plurality of nanoparticles. Theplurality of nanoparticles have a lower thermal conductivity than theinterbonded grains of hard material.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of thedisclosure, various features and advantages of embodiments of thedisclosure may be more readily ascertained from the followingdescription of some embodiments of the disclosure when read inconjunction with the accompanying drawings, in which:

FIG. 1A is a partial cut-away perspective view illustrating anembodiment of a cutting element comprising a polycrystalline compact ofthe present disclosure;

FIG. 1B is a simplified drawing showing how a microstructure of thepolycrystalline compact of FIG. 1A may appear under magnification, andillustrates interbonded and interspersed larger and smaller grains ofhard material;

FIG. 2 includes an enlarged view of one embodiment of a low thermalconductivity nanoparticle of the present disclosure; and

FIG. 3 is a perspective view of an embodiment of a fixed-cutterearth-boring rotary drill bit that includes a plurality ofpolycrystalline compacts like that shown in FIGS. 1A and 1B.

DETAILED DESCRIPTION

The illustrations presented herein are not actual views of anyparticular polycrystalline compact, microstructure of a polycrystallinecompact, particle, cutting element, or drill bit, and are not drawn toscale, but are merely idealized representations employed to describe thepresent disclosure. Additionally, elements common between figures mayretain the same numerical designation.

As used herein, the term “drill bit” means and includes any type of bitor tool used for drilling during the formation or enlargement of awellbore and includes, for example, rotary drill bits, percussion bits,core bits, eccentric bits, bi-center bits, reamers, mills, drag bits,roller cone bits, hybrid bits, and other drilling bits and tools knownin the art.

As used herein, the term “particle” means and includes any coherentvolume of solid matter having an average dimension of about 2 mm orless. Grains (i.e., crystals) and coated grains are types of particles.As used herein, the term “nanoparticle” means and includes any particlehaving an average particle diameter of about 500 nm or less.Nanoparticles include grains in a polycrystalline material having anaverage grain size of about 500 nm or less.

As used herein, the term “polycrystalline material” means and includesany material comprising a plurality of grains or crystals of thematerial that are bonded directly together by inter-granular bonds. Thecrystal structures of the individual grains of the material may berandomly oriented in space within the polycrystalline material.

As used herein, the term “polycrystalline compact” means and includesany structure comprising a polycrystalline material formed by a processthat involves application of pressure (e.g., compaction) to theprecursor material or materials used to form the polycrystallinematerial.

As used herein, the term “inter-granular bond” means and includes anydirect atomic bond (e.g., covalent, metallic, etc.) between atoms inadjacent grains of material.

As used herein, the term “catalyst material” refers to any material thatis capable of catalyzing the formation of inter-granular bonds betweengrains of hard material during a sintering process (e.g., an HTHPprocess). For example, catalyst materials for diamond include cobalt,iron, nickel, other elements from Group VIII-A of the periodic table ofthe elements, and alloys thereof.

As used herein, the term “hard material” means and includes any materialhaving a Knoop hardness value of about 3,000 Kg_(f)/mm² (29,420 MPa) ormore. Hard materials include, for example, diamond and cubic boronnitride.

As used herein, the term “low thermal conductivity nanoparticle,” meansand includes a particle comprising a material that exhibits a bulkthermal conductivity of about one hundred watts per meter-Kelvin (100Wm⁻¹K⁻¹) or less at a temperature of 23° C. Low thermal conductivitynanoparticles include, for example, nanoparticles at least partiallyformed from alumina.

FIG. 1A is a simplified, partially cut-away perspective view of anembodiment of a cutting element 10 of the present disclosure. Thecutting element 10 comprises a polycrystalline compact in the form of alayer of hard polycrystalline material 12, also known in the art as apolycrystalline table, that is provided on (e.g., formed on or attachedto) a supporting substrate 16 with an interface 14 therebetween. Thoughthe cutting element 10 in the embodiment depicted in FIG. 1A iscylindrical or disc-shaped, in other embodiments, the cutting element 10may have any desirable shape, such as a dome, cone, chisel, etc.

In some embodiments, the polycrystalline material 12 comprisespolycrystalline diamond. In such embodiments, the cutting element 10 maybe referred to as a PDC cutting element. In other embodiments, thepolycrystalline material 12 may comprise another hard material such as,for example, polycrystalline cubic boron nitride.

FIG. 1B is an enlarged simplified view illustrating how a microstructureof the polycrystalline material 12 (FIG. 1A) of the cutting element 10may appear under magnification. As discussed in further detail below,the polycrystalline material 12 includes interbonded grains 18 of hardmaterial. The polycrystalline material 12 also includes particles 19(e.g., nanoparticles or micron-sized particles) disposed in interstitialspaces 22 between the interbonded grains 18 of hard material. Theseparticulate inclusions in the polycrystalline material 12 may lower anoverall thermal conductivity of the polycrystalline material 12.Nanoparticulate inclusions (i.e., nanoparticles) having a lower thermalconductivity than at least the interbonded grains 18 of hard materialmay be incorporated into the polycrystalline material 12 such that theoverall thermal conductivity of the polycrystalline material 12 isreduced.

The overall reduction of thermal conductivity in the polycrystallinematerial 12 (FIG. 1A) may lead to an increase in thermal stability ofthe cutting element 10. The particles 19 having a low thermalconductivity may act to insulate or slow the distribution of heat to atleast a portion of the polycrystalline material 12. For example, duringdrilling of an earth formation, a temperature of an exterior of thepolycrystalline material 12 may increase due to frictional forcesbetween the polycrystalline material 12 and the earth formation. Becauseof the reduced overall thermal conductivity of the polycrystallinematerial 12, the increased temperature may be at least partiallycontained to the exterior of the polycrystalline material 12. This mayhelp to maintain an interior portion of the polycrystalline material 12at a lower and more stable temperature. Accordingly, by insulating atleast a portion of the polycrystalline material 12, the insulatedportion of the polycrystalline material 12 may be relatively less likelyto degrade during use due to thermal-expansion mismatch between thedifferent elements within the polycrystalline material 12. Furthermore,in embodiments in which the hard material comprises diamond, a decreaseof heat transferred to at least a portion of the polycrystallinematerial 12 may decrease the susceptibility of the diamond tographitize.

In some embodiments, and as shown in FIG. 1B, the grains 18 of hardmaterial in the polycrystalline material 12 may have a uniform,mono-modal grain size distribution.

In additional embodiments, the grains 18 of the polycrystalline material12 may have a multi-modal (e.g., bi-modal, tri-modal, etc.) grain sizedistribution. For example, the polycrystalline material 12 may comprisea multi-modal grain size distribution as disclosed in at least one ofU.S. Pat. No. 8,579,052, issued Nov. 12, 2013, titled “PolycrystallineCompacts Including In-Situ Nucleated Grains, Earth-Boring ToolsIncluding Such Compacts, and Methods of Forming Such Compacts andTools;” U.S. Pat. No. 8,727,042, issued May 20, 2014; titled“Polycrystalline Compacts Having Material Disposed in InterstitialSpaces Therein, and Cutting Elements Including Such Compacts;” and U.S.Pat. No. 8,496,076, issued Jul. 30, 2013, titled “PolycrystallineCompacts Including Nanoparticulate Inclusions, Cutting Elements andEarth-Boring Tools Including Such Compacts, and Methods of Forming SuchCompacts;” the disclosure of each of which is incorporated herein in itsentirety by this reference.

As known in the art, the average grain size of grains within amicrostructure may be determined by measuring grains of themicrostructure under magnification. For example, a scanning electronmicroscope (SEM), a field emission scanning electron microscope (FESEM),or a transmission electron microscope (TEM) may be used to view or imagea surface of a polycrystalline material 12 (e.g., a polished and etchedsurface of the polycrystalline material 12). Commercially availablevision systems are often used with such microscopy systems, and thesevision systems are capable of measuring the average grain size of grainswithin a microstructure.

In some embodiments, at least some of the grains 18 of hard material maycomprise in-situ nucleated grains 18 of hard material, as disclosed inU.S. Pat. No. 8,579,052, previously incorporated herein by reference.

The interstitial spaces 22 between the grains 18 of hard material may beat least partially filled with low thermal conductivity particles 19 andwith a catalyst material.

The low thermal conductivity particles 19 disposed in the interstitialspaces 22 between the interbonded grains 18 of hard material maycomprise a material having a lower thermal conductivity than theinterbonded grains 18 of hard material. For example, the interbondedgrains 18 of hard material may have a thermal conductivity of betweenabout 500 Wm⁻¹K⁻¹ and about 2600 Wm⁻¹K⁻¹ at 23° C. The low thermalconductivity particles 19 may comprise a material that exhibits athermal conductivity of about 100 Wm⁻¹K⁻¹or less at 23° C. in bulk form,or even about 50 Wm⁻¹K⁻¹ or less at 23° C. in bulk form. In oneembodiment, the particles 19 may have a thermal conductivity of about 1Wm⁻¹K⁻¹ or less at 23° C. In another embodiment, the particles 19 mayhave a thermal conductivity of about 0.2 Wm⁻¹K⁻¹or less at 23° C., suchas particles having nano-scale layers of alumina and tungsten. Thematerial of the particles 19 may have a bulk thermal conductivity ofless than about 20% of the thermal conductivity of the interbondedgrains 18, less than about 5% of the thermal conductivity of theinterbonded grains 18, or even less than about 1% of the thermalconductivity of the interbonded grains 18. The approximate bulk thermalconductivities at 23° C. for some materials are shown below in Table 1.

TABLE 1 Approximate Thermal Conductivity Material at 23° C. (Wm⁻¹K⁻¹)Diamond (type IIa) 2300 Cubic boron nitride varies - 1300 is maxtheoretical bulk Diamond (type I) 895 Platinum 716 Silicon carbide 490Copper 401 Tungsten 174 Silicon 148 Tungsten carbide 84 Alumina(polycrystalline) 36 Titanium carbide 31 Titanium 21 Titanium dioxide(polycrystalline) 8.4 Zirconia 2.0 Silicon dioxide (polycrystalline) 1.4Selenium 0.5 Molybdenum disulfide 0.2

Thermal conductivity of a material may vary as a function oftemperature. For example, the thermal conductivity of some materials maydecrease as temperature increases. The thermal conductivity of othermaterials may increase as temperature increases. A low thermalconductivity material may be selected based on its thermal conductivityat ambient room temperature (e.g., 23° C.), thermal conductivity at anoperating temperature (e.g., 750° C.) or thermal conductivity at anyother temperature.

The low thermal conductivity material of the particles 19 may comprise,for example, one or more of elementary metals (e.g., commercially puretungsten), metal alloys (e.g., tungsten alloys), refractory metals,intermetallic compounds, ceramics (e.g., carbides, nitrides, oxides),and combinations thereof. As particular non-limiting examples, the lowthermal conductivity particles 19 may comprise at least one of aluminaand zirconia.

In some embodiments, the low thermal conductivity particles 19 may, atleast initially (prior to a sintering process used to form thepolycrystalline material 12), comprise at least two materials, as does alow thermal conductivity particle 100 illustrated in FIG. 2. Forexample, the low thermal conductivity particle 100 may include a core102 comprising a first material and at least one coating 104, 106, 108comprising at least one other material. At least one of the core 102 andthe at least one coating 104, 106, 108 comprises a low thermalconductivity material. The core 102 may comprise, for example, at leastone of alumina, zirconia, zirconium, tungsten, tungsten carbide,titanium, titanium carbide, and silicon. The core 102 may comprise asingle nanoparticle or the core 102 may comprise a plurality or clusterof smaller nanoparticles 103. The core 102, comprising one particle or aplurality of nanoparticles 103, may have a total average particle sizeof between about twenty-five nanometers (25 nm) and about seventy-fivenanometers (75 nm). For example, in one embodiment, the core 102 maycomprise a single nanoparticle of the plurality of nanoparticles 103 oftungsten carbide having an average particle size of about twenty-fivenanometers (25 nm). In another embodiment, the core 102 may comprise aplurality of nanoparticles 103 having an average particle size of abouttwo nanometers (2 nm) to about ten nanometers (10 nm), which haveagglomerated to form the core 102 having an average particle size ofabout fifty nanometers (50 nm) to about seventy-five nanometers (75 nm).The plurality of nanoparticles 103 may have a uniform average particlesize, or the plurality of nanoparticles 103 may have differing averageparticle sizes. In yet further embodiments, the plurality ofnanoparticles 103 forming the core 102 may comprise at least twomaterials. For example, in one embodiment, at least one nanoparticle ofthe plurality of nanoparticles 103 comprises tungsten carbide and atleast one nanoparticle of the plurality of nanoparticles 103 comprisesalumina. A nano-scale microstructure of two or more materials mayexhibit a lower thermal conductivity than any of the component materialsalone. For example, a nano-layered composite of alumina and tungsten mayhave a thermal conductivity of about 0.2 Wm⁻¹K⁻¹.

Each coating of the at least one coating 104, 106, 108 may have athickness of between about two nanometers (2 nm) and about fivenanometers (5 nm), such as a thickness of about two nanometers (2 nm) toabout three nanometers (3 nm). In some embodiments, each of the at leastone coating 104, 106, 108 may be conformally deposited on the core 102.In other embodiments, one or more of the coatings 104, 106, 108 may beformed partially over the core 102, or may be formed having variablethicknesses. In some embodiments, multiple coatings of the same materialmay be formed over the core 102, For example, a first coating 104, asecond coating 106, and a third coating 108 may be formed over the core102, each coating 104, 106, 108 comprising alumina, In alternativeembodiments, at least two coatings 104, 106, 108 comprising differentmaterials may be formed on the core 102. For example, in one embodiment,the first coating 104 comprising alumina may be formed over the core102, the second coating 106 comprising zirconia may be formed over thefirst coating 104, and the third coating 108 comprising alumina may beformed over the second coating 106, While FIG. 2 is illustrated ashaving three coatings 104, 106, 108 over the core 102, it is understoodthat any number of coatings may be applied to the core 102 such that thetotal particle comprises a nanoparticle, In some embodiments, coatings104, 106, 108 may be applied such that the resulting particle 100 ismicron sized (i.e., larger than 500 nm). In further embodiments,micron-sized clusters formed of at least two nanoparticles, like theparticle 100 of FIG. 2, may be conglomerated and coated eitherindividually or in combination and incorporated into the polycrystallinematerial 12.

By way of example and not limitation, processes such as liquid sol-gel,flame spray pyrolysis, chemical vapor deposition (CVD), physical vapordeposition (PVD) (e.g., sputtering), and atomic layer deposition (ALD),may be used to provide the at least one coating 104, 106, 108 on thecore 102. Other techniques that may be used to provide the at least onecoating 104, 106, 108 on the core 102 include colloidal coatingprocesses, plasma coating processes, microwave plasma coating processes,physical admixture processes, van der Waals coating processes, andelectrophoretic coating processes. In some embodiments, the at least onecoating 104, 106, 108 may be provided on the core 102 in a fluidized bedreactor (not shown).

Referring again to FIGS. 1A and 1B, the volume occupied by the lowthermal conductivity particles 19 in the polycrystalline material 12 maybe in a range extending from about 0.01% to about 50% of the volume ofthe polycrystalline material 12. The weight percentage of the particles19 in the polycrystalline material 12 may be in a range extending fromabout 0.1% to about 10% by weight.

Some of the low thermal conductivity particles 19 may be mechanicallybonded to the grains 18 of hard material after the sintering process(e.g., an HPHT process) used to form the polycrystalline material 12.

In some embodiments, the polycrystalline material 12 may also include acatalyst material 24 disposed in interstitial spaces 22 between theinterbonded grains 18 of the polycrystalline hard material and betweenthe particles 19. The catalyst material 24 may comprise a catalyst usedto catalyze formation of inter-granular bonds 26 between the grains 18of hard material in the polycrystalline material 12. In otherembodiments, however, the interstitial spaces 22 between the grains 18and the particles 19 in some or all regions of the polycrystallinematerial 12 may be at least substantially free of such a catalystmaterial 24. In such embodiments, the interstitial spaces 22 maycomprise voids filled with gas (e.g., air).

In embodiments in which the polycrystalline material 12 comprisespolycrystalline diamond, the catalyst material 24 may comprise a GroupVIII-A element iron, cobalt, or nickel) or an alloy thereof, and thecatalyst material 24 may comprise between about one tenth of one percent(0.1%) and about ten percent (10%) by volume of the hard polycrystallinematerial 12. In additional embodiments, the catalyst material 24 maycomprise a carbonate material such as a carbonate of one or more ofmagnesium, calcium, strontium, and barium. Carbonates may also be usedto catalyze the formation of polycrystalline diamond.

The layer of hard polycrystalline material 12 of the cutting element 10may be formed using a high-temperature/high-pressure (HTHP) process.Such processes, and systems for carrying out such processes, aregenerally known in the art. In some embodiments, the polycrystallinematerial 12 may be formed on a supporting substrate 16 (as shown in FIG.1A) of cemented tungsten carbide or another suitable substrate materialin a conventional HTHP process of the type described, by way ofnon-limiting example, in U.S. Pat. No. 3,745,623, titled “Diamond Toolsfor Machining,” issued Jul. 17, 1973, or may be formed as a freestandingpolycrystalline material 12 (i.e., without the supporting substrate 16)in a similar conventional HTHP process as described, by way ofnon-limiting example, in U.S. Pat. No. 5,127,923, titled “CompositeAbrasive Compact Having High Thermal Stability,” issued Jul. 7, 1992,the disclosure of each of which is incorporated herein in its entiretyby this reference. In some embodiments, the catalyst material 24 may besupplied from the supporting substrate 16 during an HTHP process used toform the polycrystalline material 12. For example, the substrate 16 maycomprise a cobalt-cemented tungsten carbide material. The cobalt of thecobalt-cemented tungsten carbide may serve as the catalyst material 24during the HTHP process. Furthermore, in some embodiments, the lowthermal conductivity particles 19 also may be supplied from thesupporting substrate 16 during an HTHP process used to form thepolycrystalline material 12. For example, the substrate 16 may comprisea cobalt-cemented tungsten carbide material that also includes lowthermal conductivity particles 19 therein. The cobalt and the lowthermal conductivity particles 19 of the substrate 16 may diffuse intothe interstitial spaces 22 between the grains 18 of hard material.

To form the polycrystalline material 12 in an HTHP process, aparticulate mixture comprising particles (e.g., grains) of hard materialand low thermal conductivity particles 100 (FIG. 2) may be subjected toelevated temperatures (e.g., temperatures greater than about 1,000° C.)and elevated pressures (e.g., pressures greater than about 5.0gigapascals (GPa)) to form inter-granular bonds 26 between the particlesof hard material and the particles 100, thereby forming the interbondedgrains 18 of hard material and the particles 19 of the polycrystallinematerial 12. In some embodiments, the particulate mixture may besubjected to a pressure greater than about 6.0 GPa and a temperaturegreater than about 1,500° C. in the HTHP process.

In embodiments in which a carbonate catalyst material 24 (e.g., acarbonate of one or more of magnesium, calcium, strontium, and barium)is used to catalyze the formation of polycrystalline diamond, theparticulate mixture may be subjected to a pressure greater than about7.7 GPa and a temperature greater than about 2,000° C.

The particulate mixture may comprise hard particles for forming thegrains 18 of hard material previously described herein. The particulatemixture may also comprise at least one of particles of catalyst material24, and low thermal conductivity particles 100 for forming the particles19 in the polycrystalline material 12. In some embodiments, theparticulate mixture may comprise a powder-like substance. In otherembodiments, however, the particulate mixture may be carried by (e.g.,on or in) another material, such as a paper or film, which may besubjected to the HTHP process. An organic binder material also may beincluded with the particulate mixture to facilitate processing.

Thus, in some embodiments, the low thermal conductivity particles 100may be admixed with the hard particles used to form the grains 18 toform a particulate mixture, which then may be sintered in an HPHTprocess.

In some embodiments, the low thermal conductivity particles 100 may beadmixed with the hard particles used to form the grains 18 of hardmaterial prior to a modified HPHT sintering process used to synthesize ananoparticulate composite that includes the low thermal conductivityparticles 100 and nanoparticles of hard material.

In some embodiments, the low thermal conductivity particles 100 may begrown on, attached to, adhered to, or otherwise connected to the hardparticles used to form the grains 18 prior to the sintering process. Thelow thermal conductivity particles 100 may be attached to the hardparticles by functionalizing exterior surfaces of at least one of thelow thermal conductivity particles 100 and the hard particles. Afterattaching the low thermal conductivity particles 100 to the hardparticles, the resulting particulate mixture may be subjected to an HPHTprocess to form a polycrystalline material 12 comprising grains of hardmaterial 18 and low thermal conductivity particles 19, as describedabove.

In additional embodiments, the low thermal conductivity particles 100may be combined with the catalyst material 24 prior to the sinteringprocess. For example, the low thermal conductivity particles 100 may begrown on, attached to, adhered to, or otherwise connected to particlesof catalyst material, and the coated particles of catalyst material maybe combined with hard particles to form the particulate mixture prior tothe sintering process. The low thermal conductivity particles 100 may beattached to the particles of catalyst material by functionalizingexterior surfaces of at least one of the low thermal conductivityparticles 100 and the catalyst particles. After attaching the lowthermal conductivity particles 100 to the catalyst particles andadmixing with hard particles, the resulting particulate mixture may besubjected to an HPHT process to form a polycrystalline material 12, asdescribed above.

In some embodiments, the low thermal conductivity particles 100 may begrown on, attached, adhered, or otherwise connected to both particles ofhard material and particles of catalyst material, and the coatedparticles may be combined to form the particulate mixture.

As previously mentioned, a particulate mixture that includes hardparticles for forming the interbonded grains 18 of hard material, lowthermal conductivity particles 100, and, optionally, a catalyst material24 (for catalyzing the formation of inter-granular bonds 26 between thegrains 18), may be subjected to an HTHP process to form apolycrystalline material 12. After the HTHP process, catalyst material24 (e.g., cobalt) and low thermal conductivity particles 19 may bedisposed in at least some of the interstitial spaces 22 between theinterbonded grains 18 of hard material.

Optionally, the catalyst material 24 may be removed from thepolycrystalline material 12 after the HTHP process using processes knownin the art. However, the removal of the catalyst material 24 may alsoresult in the removal of at least a portion of the low thermalconductivity particles 19, which may be undesirable. For example, aleaching process may be used to remove the catalyst material 24 and/orthe low thermal conductivity particles 19 from the interstitial spaces22 between the grains 18 of hard material in at least a portion of thepolycrystalline material 12. By way of example and not limitation, aportion of the polycrystalline material 12 may be leached using aleaching agent and process such as those described more fully in, forexample, U.S. Pat. No. 5,127,923, previously incorporated herein byreference, and U.S. Pat. No. 4,224,380, titled “Temperature ResistantAbrasive Compact and Method for Making Same,” issued Sep. 23, 1980, thedisclosure of which is incorporated herein in its entirety by thisreference. Specifically, aqua regia (a mixture of concentrated nitricacid (HNO₃) and concentrated hydrochloric acid (HCl)) may be used to atleast substantially remove catalyst material 24 and/or low thermalconductivity nanoparticles from the interstitial spaces 22. It is alsoknown to use boiling hydrochloric acid (HCl) and boiling hydrofluoricacid (HF) as leaching agents. One particularly suitable leaching agentis hydrochloric acid (HCl) at a temperature of above 110° C., which maybe provided in contact with the polycrystalline material 12 for a periodof about two (2) hours to about sixty (60) hours, depending upon thesize of the body of polycrystalline material 12. After leaching thepolycrystalline material 12, the interstitial spaces 22 between theinterbonded grains 18 of hard material within the polycrystallinematerial 12 subjected to the leaching process may be at leastsubstantially free of catalyst material 24 used to catalyze formation ofinter-granular bonds 26 between the grains in the polycrystallinematerial 12. Only a portion of the polycrystalline material 12 may besubjected to the leaching process, or the entire body of thepolycrystalline material 12 may be subjected to the leaching process.

In additional embodiments of the present disclosure, low thermalconductivity particles 19, 100 may be introduced into the interstitialspaces 22 between interbonded grains 18 of hard, polycrystallinematerial 12 after the catalyst material 24 and any other material in theinterstitial spaces 2.2 has been removed from the interstitial spaces 22(e.g., by a leaching process). For example, after subjecting apolycrystalline material 12 to a leaching process, low thermalconductivity particles 19, 100 may be introduced into the interstitialspaces 22 between the grains 18 of hard material in the polycrystallinematerial 12. Low thermal conductivity particles 19, 100 may be suspendedin a liquid (e.g., water and/or another solvent) to form a suspensionand the leached polycrystalline material 12 may be soaked in thesuspension to allow the liquid and the low thermal conductivityparticles 19, 100 to infiltrate into the interstitial spaces 22. Theliquid (and the low thermal conductivity particles 19, 100 suspendedtherein) may be drawn into the interstitial spaces 22 by capillaryforces. In some embodiments, pressure may be applied to the liquid tofacilitate infiltration of the liquid suspension into the interstitialspaces 22.

After infiltrating the interstitial spaces 22 with the liquidsuspension, the polycrystalline material 12 may be dried to remove theliquid from the interstitial spaces 22, leaving behind the low thermalconductivity particles 19, 100 therein. Optionally, a thermal treatmentprocess may be used to facilitate the drying process. Alternatively, aliquid precursor may be chosen such that the liquid containing lowthermal conductivity nanoparticles 103 will infiltrate the interstitialspaces 22 and solidify, holding the nanoparticles 103 in place afterdrying, curing, or other treatment.

The polycrystalline material 12 then may be subjected to a thermalprocess (e.g., a standard vacuum furnace sintering process) to at leastpartially sinter the low thermal conductivity particles 19, 100 withinthe interstitial spaces 22 in the polycrystalline material 12. Such aprocess may be carried out below any temperature that might bedetrimental to the polycrystalline material 12.

Embodiments of cutting elements 10 of the present disclosure thatinclude a polycrystalline compact comprising polycrystalline material 12formed as previously described herein, such as the cutting element 10illustrated in FIG. 1A, may be formed and secured to an earth-boringtool such as, for example, a rotary drill bit, a percussion bit, acoring bit, an eccentric bit, a reamer tool, a milling tool, etc., foruse in forming wellbores in subterranean formations. As a non-limitingexample, FIG. 3 illustrates a fixed cutter type earth-boring rotarydrill bit 36 that includes a plurality of cutting elements 10, each ofwhich includes a polycrystalline compact comprising polycrystallinematerial 12 as previously described herein. The earth-boring rotarydrill bit 36 includes a bit body 38, and the cutting elements 10, whichinclude polycrystalline compacts 12 (see FIG. 1A), are bonded to the bitbody 38. The cutting elements 10 may be brazed (or otherwise secured)within pockets formed in the outer surface of the bit body 38.

Polycrystalline hard materials that include low thermal conductivitynanoparticles in interstitial spaces between the interbonded grains ofhard material, as described hereinabove, may exhibit improved thermalstability, improved mechanical durability, or both improved thermalstability and improved mechanical durability relative to previouslyknown polycrystalline hard materials. By including the low thermalconductivity nanoparticles in the interstitial spaces between theinterbonded grains of hard material, less catalyst material may bedisposed in interstitial spaces between the grains in an ultimatepolycrystalline hard material, and the thermal conductivity of thepolycrystalline material may be reduced, which may improve one or bothof the thermal stability and the mechanical durability of the ultimatepolycrystalline hard material.

Additional non-limiting example embodiments of the disclosure aredescribed below.

Embodiment 1

A polycrystalline compact comprising a plurality of grains of hardmaterial having a first thermal conductivity at 23° C. and a pluralityof nanoparticles having a second thermal conductivity at 23° C. disposedin interstitial spaces between the plurality of grains of hard material,The second thermal conductivity is less than about 0.2 times the firstthermal conductivity.

Embodiment 2

The polycrystalline compact of Embodiment 1, wherein the plurality ofgrains of hard material comprises a plurality of grains of diamond.

Embodiment 3

The polycrystalline compact of Embodiment 1 or Embodiment 2, wherein thesecond thermal conductivity is less than about 50 Wm⁻¹K⁻¹,

Embodiment 4

The polycrystalline compact of Embodiment 3, wherein the second thermalconductivity is about 0.2 Wm⁻¹K⁻¹.

Embodiment 5

The polycrystalline compact of any of Embodiment 1 through Embodiment 4,further comprising a catalyst material in the interstitial spacesbetween the plurality of grains of hard material.

Embodiment 6

The polycrystalline compact of any of Embodiment 1 through Embodiment 5,wherein the plurality of nanoparticles comprises alumina,

Embodiment 7

The polycrystalline compact of any of Embodiment 1 through Embodiment 6,wherein each nanoparticle of the plurality of nanoparticles comprises acore comprising a first material and at least one coating on the core.The at least one coating comprises a second, different material.

Embodiment 8

The polycrystalline compact of Embodiment 7, wherein the core comprisesat least two particles.

Embodiment 9

The polycrystalline compact of Embodiment 7 or Embodiment 8, wherein thecore comprises tungsten carbide and the at least one coating on the corecomprises alumina.

Embodiment 10

The polycrystalline compact of any of Embodiment 7 through Embodiment 9,wherein the at least one coating on the core comprises a first coatingcomprising alumina, a second coating comprising zirconia, and a thirdcoating comprising alumina.

Embodiment 11

The polycrystalline compact of any of Embodiment 1 through Embodiment10, wherein the plurality of nanoparticles occupies from about 0.01% toabout 50% by volume of the polycrystalline compact.

Embodiment 12

The polycrystalline compact of any of Embodiment 1 through Embodiment11, further comprising a substrate bonded to the plurality of grains ofhard material.

Embodiment 13

An earth-boring tool comprising a polycrystalline compact. Thepolycrystalline compact has a plurality of grains of hard materialhaving a first thermal conductivity at 23° C. and a plurality ofnanoparticles having a second thermal conductivity at 23° C. disposed ininterstitial spaces between the plurality of grains of hard material.The second thermal conductivity is less than about 0.2 times the firstthermal conductivity.

Embodiment 14

The earth-boring tool of Embodiment 13, wherein the earth-boring tool isa fixed-cutter rotary drill bit.

Embodiment 15

A method of forming a polycrystalline compact, comprising combining aplurality of hard particles having a first thermal conductivity at 23°C. and a plurality of nanoparticles having a second thermal conductivityat 23° C. to form a mixture and sintering the mixture to form apolycrystalline hard material comprising a plurality of interbondedgrains of hard material. The second thermal conductivity is less thanabout 0.2 times the first thermal conductivity.

Embodiment 16

The method of Embodiment 15, wherein combining a plurality of hardparticles and a plurality of nanoparticles to form a mixture comprisescombining a plurality of diamond particles and a plurality ofnanoparticles to form the mixture.

Embodiment 17

The method of Embodiment 15 or Embodiment 16, wherein combining aplurality of hard particles having a first thermal conductivity at 23°C. and a plurality of nanoparticles having a second thermal conductivityat 23° C. to form a mixture comprises combining a plurality of hardparticles with nanoparticles comprising a material having a thermalconductivity less than about 50 Wm⁻¹K⁻¹.

Embodiment 18

The method of any of Embodiments 15 through 17, wherein combining aplurality of hard particles having a first thermal conductivity at 23°C. and a plurality of nanoparticles having a second thermal conductivityat 23° C. to form a mixture comprises combining a plurality of hardparticles with nanoparticles comprising alumina.

Embodiment 19

The method of any of Embodiments 15 through 18, further comprisingadding a catalyst to the mixture, the catalyst selected to promoteformation of inter-granular bonds between the grains of hard material.

Embodiment 20

The method of any of Embodiments 15 through 19, wherein sintering themixture comprises sintering the mixture in an HTHP process.

Embodiment 21

The method of any of Embodiments 15 through 20, further comprisingforming a nanoparticle of the plurality of nanoparticles comprisingcoating a core comprising a first material with a second material. Thesecond material comprises the material having a lower thermalconductivity than the plurality of hard particles.

Embodiment 22

A method of forming a cutting element, comprising infiltratinginterstitial spaces between interbonded grains of hard material in apolycrystalline material with a plurality of nanoparticles. Theplurality of nanoparticles have a thermal conductivity at 23° C. of lessthan about 20% of a thermal conductivity at 23° C. of the interbondedgrains of hard material.

Embodiment 23

The method of Embodiment 22, wherein infiltrating interstitial spacesbetween interbonded grains of hard material in a polycrystallinematerial with a plurality of nanoparticles comprises infiltratinginterstitial spaces between interbonded diamond grains with a pluralityof nanoparticles,

Embodiment 24

The method of Embodiment 22 or Embodiment 23, wherein infiltratinginterstitial spaces between interbonded grains of hard material in apolycrystalline material with a plurality of nanoparticles comprisesinfiltrating interstitial spaces between interbonded grains of hardmaterial in a polycrystalline material with a material having a thermalconductivity of less than about 50 Wm⁻¹K⁻¹.

Embodiment 25

The method of any of Embodiments 22 through 24, wherein infiltratinginterstitial spaces between interbonded grains of hard material in apolycrystalline material with a plurality of nanoparticles comprisesinfiltrating interstitial spaces between interbonded grains of hardmaterial in a polycrystalline material with nanoparticles comprisingalumina.

While the present disclosure has been described herein with respect tocertain embodiments, those of ordinary skill in the art will recognizeand appreciate that it is not so limited, Rather, many additions,deletions, and modifications to the embodiments described herein may bemade without departing from the scope of the invention as hereinafterclaimed, including legal equivalents. In addition, features from oneembodiment may be combined with features of another embodiment whilestill being encompassed within the scope of the invention ascontemplated by the inventor. Further, embodiments of the disclosurehave utility with different and various bit profiles, as well as variouscutting element types and configurations.

What is claimed is:
 1. A polycrystalline compact, comprising: aplurality of grains of hard material; and a plurality of nanoparticlesdisposed in interstitial spaces between the plurality of grains of hardmaterial, wherein each nanoparticle of the plurality comprises: a corecomprising a first material; and at least one oxide material on thecore, the at least one oxide material different from the first material.2. The polycrystalline compact of claim 1, wherein the plurality ofgrains of hard material comprises a plurality of grains of diamond. 3.The polycrystalline compact of claim 1, wherein the second thermalconductivity is less than about 50 Wm⁻¹K⁻¹.
 4. The polycrystallinecompact of claim 1, further comprising a catalyst material in theinterstitial spaces between the plurality of grains of hard material. 5.The polycrystalline compact of claim 1, wherein the grains of hardmaterial exhibit a first thermal conductivity at 23° C. and thenanoparticles exhibit a second thermal conductivity at 23° C., whereinthe second thermal conductivity is less than about 0.2 times the firstthermal conductivity.
 6. The polycrystalline compact of claim 1, whereinthe core comprises at least two particles.
 7. The polycrystallinecompact of claim 1, wherein the core comprises tungsten carbide and theat least one oxide material on the core comprises alumina.
 8. Thepolycrystalline compact of claim 5, wherein the at least one oxidematerial on the core comprises a first oxide material comprisingalumina, a second oxide material comprising zirconia, and a third oxidematerial comprising alumina.
 9. The polycrystalline compact of claim 1,wherein the plurality of nanoparticles occupies from about 0.01% toabout 50% by volume of the polycrystalline compact.
 10. Thepolycrystalline compact of claim 1, further comprising a substratebonded to the plurality of grains of hard material.
 11. An earth-boringtool comprising the polycrystalline compact of claim
 1. 12. Theearth-boring tool of claim 11, wherein the earth-boring tool is afixed-cutter rotary drill bit.
 13. A method of forming a polycrystallinecompact, comprising: combining a plurality of hard particles with aplurality of nanoparticles to form a mixture, each nanoparticle of theplurality of nanoparticles comprising: a core comprising a firstmaterial and; at least one oxide material on the core, the at least oneoxide material different from the first material; and sintering themixture to form a polycrystalline hard material comprising a pluralityof interbonded grains of hard material.
 14. The method of claim 13,wherein combining a plurality of hard particles with a plurality ofnanoparticles to form a mixture comprises combining a plurality ofdiamond particles with a plurality of nanoparticles to form the mixture.15. The method of claim 13, wherein combining a plurality of hardparticles with a plurality of nanoparticles to form a mixture comprisescombining a plurality of hard particles exhibiting a first thermalconductivity at 23° C. with nanoparticles exhibiting a second thermalconductivity at 23° C., wherein the second thermal conductivity is lessthan about 0.2 times the first thermal conductivity.
 16. The method ofclaim 15, wherein combining a plurality of hard particles having a firstthermal conductivity at 23° C. with a plurality of nanoparticles havinga second thermal conductivity at 23° C. to form a mixture comprisescombining a plurality of hard particles with nanoparticles comprising amaterial having a thermal conductivity less than about 50 Wm⁻¹K⁻¹. 17.The method of claim 13, further comprising adding a catalyst to themixture, the catalyst selected to promote formation of inter-granularbonds between the grains of hard material.
 18. A method of forming acutting element, comprising infiltrating interstitial spaces betweeninterbonded grains of hard material in a polycrystalline material with aplurality of nanoparticles, each nanoparticle of the plurality ofnanoparticles comprising: a core comprising a first material and; atleast one oxide material on the core, the at least one oxide materialdifferent from the first material.
 19. The method of claim 18, whereininfiltrating interstitial spaces between interbonded grains of hardmaterial in a polycrystalline material with a plurality of nanoparticlescomprises infiltrating interstitial spaces between interbonded diamondgrains with a plurality of nanoparticles.
 20. The method of claim 18,wherein infiltrating interstitial spaces between interbonded grains ofhard material in a polycrystalline material with a plurality ofnanoparticles comprises infiltrating interstitial spaces betweeninterbonded grains of hard material in a polycrystalline material with amaterial having a thermal conductivity of less than about 50 Wm⁻¹K⁻¹.